This invention relates to the field of protection of electronic circuitry. In particular, the invention comprises a device which protects electronic circuitry from damage due to a nuclear explosion.
A nuclear explosion causes a brief, sudden, intense flux of neutrons. A large flux density of neutrons can be disastrous for semiconductor devices such as microchips. The flux of neutrons tends to turn semiconductor switches "on". Thus, a nuclear explosion, or "nuclear event", presents two distinct problems. First, by randomly actuating semiconductor switches in a circuit, the neutron flux effectively causes total loss of control over the circuit. Secondly, when most or all of the semiconductor switches have been actuated at once, abnormally large currents are likely to flow, and these currents can destroy the entire circuit.
A typical power supply system includes a main power supply which provides control voltages to a plurality of other power supplies, each of which is used to supply power to a particular sub-circuit. The power supplies in the system may be controlled by a pulse-width modulated (PWM) signal, and the control voltages provide power to the PWM circuits in each power supply in the system.
During a nuclear event, it is necessary to disable not only the main power supply but also all of the subsidiary supplies in the system. It is especially important to discharge the output filter capacitors for each supply, because the charge on these capacitors is large and potentially damaging, especially when combined with the effects of a nuclear event.
Protection devices for electronic circuits have been known in the prior art. Typical circuits use silicon controlled rectifiers and zener diodes to clamp the output of a power supply to a predetermined level, upon detection of an excessive voltage condition. However, the response time of such circuits is too long to provide adequate protection from the very sudden neutron flux that would be experienced during a nuclear event. Furthermore, such protective circuits may be dependent on the operation of circuitry which itself becomes disabled during a nuclear event.
The present invention provides a circuit which automatically and rapidly disables a power supply system upon detection of a nuclear event, and which automatically and periodically attempts to re-start the system, on the assumption that the burst of neutrons may have been abated. The invention can be used to control power supply systems used in many different applications. For example, thermal imaging systems, microprocessors, motor drives, and other devices, can all be protected from damage by using the present invention.